1. Field of the Invention
The present invention relates generally to ultrasonic probes and, more particularly, to transthoracic ultrasound imaging probes.
2. Related Art
The use of ultrasound for medical imaging is well-known. Since its introduction, advances in technology and clinical practice have made ultrasound a leading medical diagnostic imaging modality. Ultrasound provides high-resolution real-time imaging without the use of ionizing radiation which is required for other techniques such as X-ray imaging. In addition, modern ultrasound equipment is relatively inexpensive and portable. This cost-effectiveness and portability has resulted in the widespread application of ultrasound imaging to observe a wide range of physical conditions and to identify many types of disorders.
For example, ultrasound imaging is commonly used in surgical and intravascular applications, as well as in guiding other interventional procedures. In addition, ultrasound is used in such clinical applications as obstetrics and gynecology, general abdominal imaging, vascular imaging and cardiology. This latter application, which is of significance in the present application, is referred to as echocardiography.
Various techniques have been developed for ultrasound cardiac imaging. Some conventional methods include invasive steps in which there is some disruption or alteration of the vascular and/or cardiac systems. Other conventional methods are directed to imaging the heart during surgical operations when the heart is exposed. These invasive approaches are limited in their application for a variety of reasons, including patient discomfort, increased risk of complications, and the need to use sterilized and expensive medical devices.
Non-invasive echocardiographic methods also exist. Conventional transthoracic ultrasound imaging probes have been developed for this purpose primarily because surgical imaging probes were found to be inappropriate for use in non-invasive or transthoracic cardiac imaging. The acoustical energy generated by the small transducers of invasive imaging probes is generally insufficient to penetrate the body and intervening anatomical structures.
Conventional transthoracic ultrasound imaging probes are generally elongate probes having an ultrasound transducer located on the distal end of the probe body. The probes are generally constructed of a hard plastic casing to facilitate cleaning of the probes. Typically, the probe is maneuvered so that the transducer is positioned adjacent to an external location on the body where acoustic imaging is facilitated by the underlying tissue. In cardiac imaging, these locations, referred to as an imaging windows, are typically between the ribs of the patient.
There are four primary echocardiographic imaging windows: the suprasternal, subcostal, parasternal and apical windows. The appropriateness of each imaging window depends upon the structures, functions and conditions to be diagnosed as well as the type and size of the patient. Each imaging window provides an opportunity to image a specific portion or characteristic of the cardiac structures and/or functions depending on the portion of the heart which is nearest the imaging window, the angle of the probe at that window, and the intervening structures which may interfere with imaging the desired cardiac structures. In addition, the utility of certain windows is limited by the size and condition of the patient. Accordingly, specific windows are used to diagnose specific conditions and disorders of specific patients.
When performing transthoracic echocardiographic procedures, the patient is generally lying horizontally on his or her left side. While the patient lies still in an appropriate position, the sonographer applies the transducer to a predetermined imaging window on the patient's body. The transducer must be positioned at the correct location and in the correct orientation for the selected imaging window for it to send the ultrasound signals at the proper angle so as to obtain clear and accurate cardiac images.
To place the probe in the proper position, the sonographer must maintain control over the probe throughout the echocardiograph procedure. This often requires the sonographer to apply a large gripping force to the probe casing. Two techniques are commonly used. Left-handed scanning calls for holding the ultrasound probe with the left hand while manipulating the ultrasound imaging system controls with the right hand. Conversely, right-handed scanning calls for using the right hand to control the ultrasound probe while manipulating the imaging system with the left hand. Typically, a right-handed sonographer is positioned behind the horizontally-positioned patient. The sonographer must reach completely around the right side of the patient to properly position the ultrasound probe at one of the ultrasound imaging windows. The gripping force that must be applied by the sonographer to push and hold the probe in the proper location and orientation is significant in such an awkward position. In other situations, the sonographer may have to work in environments even more awkward, such as operating rooms, intensive care units, etc.
In addition, a large percentage of patients on which echocardiography is performed tend to be obese. With such patients, the sonographer must apply a significant gripping force while maneuvering the probe despite layers of fat. Furthermore, the use of coupling gel interferes with the sonographers'capability to securely hold and control the ultrasound probe when the coupling gel migrates from the acoustic path onto the handle surfaces.
It is not uncommon for the sonographer to repeatedly perform procedures to insure that the images that were obtained were accurate representations of the cardiac condition and not artifacts due to improper placement or orientation of the probe. Therefore, occupational injuries to the sonographer may occur due to the continual application of a significant gripping force to the ultrasound probe while performing many such procedures throughout a given time period. Such occupational injuries can increase the cost and decrease the availability of the procedure.
Conventional probes generally have surface features to enable the sonographer to establish the proper orientation of the probe. For example, some ultrasound probes have curves, scallops or ridges, while other probes have a localized feature such as a line, rib, flute, button or some other feature on one side of the transducer.
Although the orientation-related features of conventional ultrasound probes may provide some incidental assistance to the sonographer to maintain control over the probe, these features do not provide significant assistance and are ancillary to the purpose of establishing proper orientation of the probe.
What is needed, therefore, is a means for assisting the sonographer in controlling the ultrasound probe in various operating scenarios, including different relative positions of the sonographer and the patient and the presence of coupling gel. The resulting ultrasound probe should also accommodate all traditional viewing windows, regardless of the physical condition of the patient. The probe should be comfortable to hold and easily controllable with minimal gripping force in all of the noted environments to reduce fatigue and the occurrence of occupational injuries.